Quitting Party at Boss PQ

This is only interesting if you get full exp for everyone, (NOT the bonus exp for each round.) and points as if you were soloing.

And when you reach the break, does it kick you out if you don't have a party, or does it wait until you remake the party before you can continue, and then you can just un-party again?

You get the exp both from killing the boss and moving to the next stage. When you break it doesn't kick you out, but it's hard to remake an entire party at the break area